1. Field of the Invention
The present invention relates to a device for controlling a compressor, and more particularly to an apparatus for controlling a compressor for reversible, dual capacity operation.
2. Description of the Related Art
Economic advantages are provided in the operation of an air conditioning system if the system is capable of operating efficiently at a lowered volumetric displacement on mild days and at a higher volumetric displacement on hot days. Running the system at a lower capacity reduces the power consumption and increases the life of the system.
Typically, multiple compressors or a single dual capacity compressor have been used for this situation. The dual capacity compressor operates two pistons in the forward direction and one piston in the reverse direction. Examples of such a compressor is disclosed in U.S. Pat. No. 4,248,503 and allowed patent application 09/099,013, which are expressly incorporated by reference. A reversible compressor motor is used to run the compressor in the forward or reverse direction. Typically, capacity choice is controlled by a standard mechanical or electronic two stage thermostat.
The present invention in one form thereof involves a device for controlling a reversible compressor. The device provides a microprocessor-based control circuit including a pressure switch that differentiates between high and low load conditions and generates a control signal representing such conditions. During high load conditions the motor is controlled to rotate the compressor in the forward direction using dual cylinders and during low load conditions to rotate the compressor in the reverse direction using a single cylinder. The switchover occurs with the compressor at rest and start against equalized pressure, a time delay is introduced to effect this. During the time delay induced off time, a signal is generated to energize a relay to effectuate a switch in the wiring to allow direction reversal.
The present invention provides a reversible, dual capacity compressor system. The system comprises a reversible compressor, a pressure sensor coupled to the compressor, and a control assembly electrically coupled to the compressor and the pressure sensor. The reversible compressor operates at a first capacity when the compressor rotates in a first direction and at a second capacity when the compressor rotates in a second direction. The first capacity is greater than the second capacity. The pressure sensor generates a high pressure signal and a low pressure signal, whereby a high pressure signal indicates a high load condition and a low pressure signal indicates a low load condition. The control assembly controls the compressor to rotate in the first direction when receiving the high pressure signal from the pressure sensor and to rotate in the second direction when receiving the low pressure signal from the pressure sensor.
An advantage of the present invention is that a single stage thermostat can be used to control life reversible compressor.